An iron fist/hand (in a velvet glove) phrase
Someone who looks gentle and sweet but in fact is severe and forceful
She is an iron hand in a velvet glove! She is actually a severe teacher.
Laura seems like a gentle lady, but she's an iron fist in a velvet glove.
Don't make fun of her! She's an iron fist in a velvet glove!
The way Tom monitors the class seems to be an iron fist in a velvet glove.
This idiom means that someone does not share what they think or feel with others.
Try to hide and deny something that is embarrassing, unappealing, or damaging to one's reputation
To deliberately hide one's true nature, intentions or purposes
1. If you hide away, you go somewhere so that no one can find you.
2. If you hide someone or something away, you put them in a place where people cannot find them.
The origin of this idiom is not clear but a source said that it came from the Latin 'Suaviter in modo, fortiter in re', which means something similar.